A stent graft is a tube composed of fabric generally supported by a polymeric or metallic structure. It can be used for a variety of conditions, most commonly in blood vessels to reinforce a weak spot in an artery, such as an aneurism. It may also be used in other locations, such as, for example, the esophagus. Typically, a stent graft is made of a radially expandable reinforcement structure, for example, a plurality of annular rings, and a cylindrically shaped layer of graft material. Representative examples of stent grafts include, for example, those disclosed in U.S. Pat. Nos. 6,123,722, 7,377,937, 7,691,141, 7,806,917, 7,914,568, 8,080,051 and 8,100,960.
The most common type of vascular stent graft is an endovascular stent graft used to treat an abdominal aortic aneurism or a thoracic aortic aneurism. The endovascular stent graft is placed inside the aneurysm and acts as a false lumen through which blood can travel, instead of flowing into the aneurysm sac, and is designed to help prevent an aneurism from bursting. Endovascular stent grafts are also used in dialysis grafts and dialysis fistulas to treat obstructions or aneurysms that occur at the site of vascular access required for hemodialysis treatments in kidney failure patients.
To perform endovascular stent graft implantations, a surgeon will insert the stent graft into the blood vessel at the location of the aneurism in order to reduce the pressure on the blood vessel walls at the site of the aneurism. Such stent grafts have been used widely for many years and are well known. Unfortunately, such endovascular stent grafts are sometimes subject to failure. One failure that may occur is leaking of blood into the aneurysm sac; a condition referred to as an endoleak, of which there are 5 different types. A Type I Endoleak occurs when blood flows between the stent graft and the blood vessel wall; typically at the proximal (often renal) or distal (often iliac) end of the graft. This complication may also occur as a result of movement of the graft away from the desired location, sometimes called migration. Type II Endoleaks occur when blood flows backwards (retrograde) into the aneurysm sac from arteries originating from the aneurysm sac itself (typically the lumbar, testicular or inferior mesenteric arteries). Type III endoleaks occur when blood leaks between the junction sites of “articulated” or “segmented” stent grafts; these multi-component stent grafts are inserted as separate segments which are then assembled inside the artery into their final configuration. Detecting and confirming accurate assembly and fluid-tight contact between the different segments is difficult and current verification methods of correct assembly are suboptimal. Type IV Endoleaks occur when cracks or defects develop in the stent graft fabric and blood is able to leak directly through the graft material. Lastly, Type V Endoleaks are leakage of blood into the aneurysm sac of an unknown origin. Regardless of their cause, endoleaks are frequently a medical emergency and early detection, characterization and monitoring of them is an important unmet medical need.
Other complications of stent graft placement include partial blockage of the blood flowing through the stent graft (stenosis), detachment, rupture, fabric wear (durability), kinking, malpositioning, and systemic cardiovascular disorders (myocardial infarction, congestive heart failure, arrhythmias, renal failure). Presently, detecting such complications prior to their occurrence or early in their development is difficult or, in many cases, impossible.
The present invention discloses novel stent grafts which overcome many of the difficulties of previous stent grafts, methods for constructing and utilizing these novel stent grafts, and further provides other related advantages.